Hydrophobic CuO Nanosheets Functionalized with Organic Adsorbates.

A new class of hydrophobic CuO nanosheets is introduced by functionalization of the cupric oxide surface with p-xylene, toluene, hexane, methylcyclohexane, and chlorobenzene. The resulting nanosheets exhibit a wide range of contact angles from 146° (p-xylene) to 27° (chlorobenzene) due to significant changes in surface composition induced by functionalization, as revealed by XPS and ATR-FTIR spectroscopies and computational modeling. Aromatic adsorbates are stable even up to 250-350 °C since they covalently bind to the surface as alkoxides, upon reaction with the surface as shown by DFT calculations and FTIR and 1H NMR spectroscopy. The resulting hydrophobicity correlates with H2 temperature-programmed reduction (H2-TPR) stability, which therefore provides a practical gauge of hydrophobicity.